A variety of medical devices are used for chronic, e.g., long-term, delivery of electrical stimulation therapy to patients suffering from conditions that range from chronic pain, tremor, Parkinson's disease, and epilepsy, to urinary or fecal incontinence, sexual dysfunction, obesity, spasticity, and gastroparesis. As an example, electrical stimulation generators are used for chronic delivery of electrical stimulation therapies such as neurostimulation, spinal cord stimulation, muscle stimulation, target organ stimulation, or the like. Typically, such devices provide therapy continuously or periodically according to parameters contained within a program. A program may comprise respective values for each parameter in a set of therapeutic parameters specified by a clinician. For example, a program may define characteristics of the electrical pulses defining the stimulation waveform, including pulse width, pulse frequency, constant voltage or constant current amplitude, and electrode polarity (anode or cathode). Traditional neurological stimulators generate a constant voltage or constant current output pulse that is typically programmable for a predefined constant current or voltage stimulus amplitude and pulse width.